Subtracting Integers - How does subtraction relate to addition?

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Objective

Students will be able to subtract integers by adding the additive inverse.

Big Idea

Subtraction does not have to be any harder than addition – students will turn all subtraction problems into addition problems and use the rules they have already mastered!

Launch

5 minutes

Opener:  As students enter the room, they will immediately pick up and begin working on the opener.  Please see my instructional strategy clip for how openers work in my classroom (Instructional Strategy - Process for openers).  This method of working and going over the opener lends itself to allow students to construct viable arguments and critique the reasoning of others, which is mathematical practice 3.  

Learning Target:  After completion of the opener, I will address the day’s learning targets to the students.  In today’s lesson, the intended targets are, “I understand the relationship between addition and subtraction and I can subtract integers.” Students will jot the learning target down in their agendas (our version of a student planner, there is a place to write the learning target for every day). 

Explore

55 minutes

Subtracting Integers Notes:  Subtracting Integers Explore Narrative The notes begin with an inquiry activity where students will be using tools strategically through the incorporation of the number line (mathematical practice 5). Additionally, they will be looking for patterns in repeated reasoning to develop a mathematical rule for subtraction, which is mathematical practice 8. They will also be making use of the structure of a problem, by recognizing that subtracting is actually adding the opposite (mathematical practice 7). fter the group inquiry, I will bring the class back together to develop a written rule for subtraction. I am going to address subtraction as adding the additive inverse, or the opposite. Though opposite is an easier term, it is very important that students use correct vocabulary, and I will model this for them. I will include the word opposite in the rule, however, so that students visually are able to connect additive inverse with opposite. After going over the rule, I am going to model two examples with the students, first changing the problems to addition, and then using addition rules to simplify. With this topic, it is very important that students are precise when paying attention to the signs of the numbers, mathematical practice 6

Table Practice: Students will continue their work on subtracting integers by completing a few problems with their tables. The first few problems ask that students simply change the problems to equivalent addition problems, and then the students will move into solving. I will ask that students work individually for 5 minutes, and then collaborate with their groups. I want to give students time to persevere (mathematical practice 1) with the problems before their group blurts out the answers!

Summarize + Homework

5 minutes

Summary Questions:  To summarize this lesson, I am going to post 4 problems on the board, 2 addition and 2 subtraction.  The students will complete these problems on the back of their opener, and then make a pile of their openers on their table for me to collect.  The purpose of this activity is for me to get a grasp on who has it, and who needs more practice.  I will use the data from these questions to move seats around for the next class as well as differentiate their next assignment. 

Homework:  After students complete the summary questions they will begin working on their homework assignment. Philosophy on Homework